Hydraulic pneumatic system for actuating pressure



Nov. 6, 1951 R. K. SEDGWICK 2,573,993

HYDRAULIC PNEUMATIC SYSTEM FOR ACTUATING PRESSURE Filed July 10, 1948 2 SHEETS-SHEET 1 A 2 J0 J? 45 I AIR OIL.

TANK Z6 56 IN V EN TOR.

HYDRAULIC PNEUMATIC SYSTEM FOR ACTUATING PRESSURE 7 Filed July 10, 1948 Nov. 6, 1951 R. K. SEDGWICK 2 SHEETS-SHEET 2 1%? I l I U INVENTOR. Foezi fzfiecgz ad Patented Nov. 6, 1951 HYDRAULIC PNEUMATIC SYSTEM FOR ACTUATING PRESSURE RobertK. Sedgwick, Oak Park, -Ill., assignor to American Steel Foundries, Chicago, 111., a corporation of New Jersey 7 Application July 10, 1948, wam. 38,093

This invention relates to hydraulic presses and more particularly to a novel actuating circuit adapted for operation of small inexpensive hydraulic presses.

Throughout the hydraulic press industry, and particularly in the plastic molding field, there has been a demand for a small, relatively inexpensive hydraulic press for the production of small pieces involving simple pressing techniques and comparatively low tonnage. 'To meet this demand there have been designed many small presses of the laboratory type and a number of small presses constructed according to conventional designs for standard large size'p resses. Both of these types of presses have proved inadequate inasmuch as the laboratory type press is inconvenient to handle and is generally not powered, and the small presses of conventional design are necessarily expensive per unit of capacity because of the hydraulic pumps and motors required. 7

Thus this particular size range of hydraulic presses has been reluctantly neglected by press manufacturers in favor of designs and sizes which have warranted a considerable investment on the part of the purchaser. The present invention relates to a small size inexpensive hydraulic press which is power actuated and is suitable to meet the requirements of the industry.

A general object of the invention is to provide a practical and inexpensive powered hydraulic press for the above-mentioned purposes.

Another object of the invention is "to devise. an hydraulic press comprising a novel actuating system including a pneumatic intensifier or power device for developing hydraulic pressure on the pressure or working stroke of the press.

Still another object of the invention is to devise a novel actuating circuit such as above described whereby the rapid advance stroke of the press ram to the work is effected by pneumatic displacement of the hydraulic fluid in the associated reservoir and the pressure or working stroke of the ram againstthe work is effected by a pneumatic intensifier or pressure device.

A further object of the invention is to devise a circuit such as above described comprising an automatically operable, continuous intensifier for continuously advancing the ram against the work until a predetermined load is developedthereagainst. I

Still another object of the invention .is to devise an intensifier of-novel form particularly adapted for the above type-of circuit;said intensifier comprisingan air cylinder containinga double acting 2 Claims. (01.60 51) piston, each end of 'the cylinder being sealed by a head' containing an hydraulic unit including a plunger operatively connected to thepiston. The cylinder is provided with means for automatically directing compressed air alternately to opposite ends of the cylinder thereby efiecting continuous operation of the hydraulic intensifier units, until a predetermined pressure is developed against the work.

The foregoing and other objects and advantages of the invention will become apparent from a consideration of the following specification and the accompanying drawings, wherein:

Figure 1 is a fiow diagram illustrating the novel circuit;

Figure 2 is a plan view of the novel intensifier, portions thereof being broken away in Vertical section to clarify the construction;

Figure 3 is a view taken from the side of Figure 2 with portions of the structure broken away; and

Figure 4 is an end view taken from the left of Figure 2, partly in section, on the line 4-4 thereof.

Describing the invention in detail and referring first to the flow diagram of Figure 1 wherein the hydraulic piping is shown in double lines and the pneumatic piping in single lines, the system comprises an hydraulic press motor 2 including a cylinder 4 with a ram 6 reciprocal therein and adapted to actuate a platen 3 against associated work (not shown). The cylinder 3 comprises a passage l0 connected to a prefill and exhaust valve [2 having a chamber l4 adapted for connection to the passage ill and containing a valve stem IG'spring-pressed to closed position, as by a coil spring ll.' The valve stem is actuated to open position, a hereinafter described, by a plunger l8 operated by a lever 2E! pivoted at 2'2 to the valve l2. The chamber I4 is connected by an inlet port24 to an hydraulic inlet line 26 connected to a tank or reservoir '28 adapted to contain a supply of hydraulic fiuid, such as -oil. The chamber I4 is also connected by an outlet port 36 to a line 32 connected to an intensifier 34, hereinafter described in detail. The intensifier comprises a pair of hydraulic units 36 having their suction sides connected to the line 32 and their discharge sides connected to a high pressureline 38 communicating bya port 40 with the cylinder 4.

The intensifier is operated, as hereinafter discussed, by compressed pneumatic fluid, such as air, conveyed thereto by a line 42 connected to an air valve 44 which is also connected 'by a In operation of the above-described system, the

valve 44 is first actuated to rapid advance or prefill position at which compressed air is directed through the line 45 to the tank 28; and

the valve stem I6 is actuated to open position by rapid advance stroke to the work. After the ram has engaged the work under the comparatively light pressure of the hydraulic fluid in the tank 28, the stem It is closed, as shown in Figure 1, the line 25 being connected to the line 32; and the valve 44 is actuated to its full pressure position whereat compressed air is directed to the line 42 and thence to an air cylinder 54 of the intensifier 34 operating the units 36, as hereinafter discussed, to urge high pressure fluid through the main pressure line 38 into the passage 45! thereby actuating the ram 6 under full pressure against the work until a predetermined pressure has been developed thereagainst.

The ram 6 is released by actuation of the valve 44 to neutral position whereat the lines 42 and 46 are connected to the exhaust line 48 thereby terminating operation of the intensifier 3d and releasing pneumatic pressure on the hydraulic fluid in the tank 23. Thereafter the operator actuates the stem It to open position accommodating discharge of the pressure fluid within" the cylinder 4 to the tank 28 whereupon the pressure on the ram is relieved and, in the vertical position illustrated in Figure l, the ram is returned by operation of gravity to position shown in the drawings.

Referring now to Figures 2 to 4 inclusive, the intensifier 34 is shown in detail and comprises the above-mentioned air cylinder 54 which is provided with brackets 56 adapted for convenien mounting on a press frame (not shown) i The cylinder 54 contains a double acting air piston 58 connected at opposite sides thereof to a pair of identical hydraulic plungers 50 which, as best seen in Figure 3, are press fitted into cornplementary openings in the piston 58; 7

Each end of the cylinder 54 is sealed by a head 52 having a flange 54 secured as by screws 86 to ball check valve E2 adapted to open on the suc{ tion stroke of the plunger and adapted to close on the discharge stroke of the plunger. The ball valve i2 is limited in its movement to open position by a stem 14 within a chamber 16 containing a plug 18 carrying the stem 14. The chamber 68 is also connected to an outlet or discharge port 85 equipped with a ball check 'valve 82 operable within a chamber 84 closed by a plug 83 which carries a stem 88 adapted to limit movement of the ball 82 to open position. The chamber 84'is connected to a discharge port 90 whereby on the pressure stroke of the plunger 60, the ball 82 is forced to open position accommodating discharge of hydraulic fluid from the chamber 68 to the discharge port 90.

Each head 62 is preferably provided with a plunger bushing 92 having a machined fluid-tight fit with the plunger 66, and the head is provided with an annular groove 94 surrounding the outer diameter of the bushing to collect leakage oil which is drained from the groove 94 by a drain port 96.

The air piston 58 during actuation of the intensifier 34 is automatically reciprocated by a valve mechanisrn, generally designated 98 (Figure'2) This mechanism comprises a cylindrical valve chamber or bore I00 in a boss I82 formed on the side of the cylinder 54. The bore I00 contains a valve stem I04 having four spaced lands or spools I06, I08, III], and I12 slidably fitted within the bore H38 in substantially fluid-tight engagement therewith. Compressed air is admitted to the bore I00 through a port I14 connected"to the before-mentioned air line 42, and air is exhausted from the bore by exhaust or discharge lines H5 and I I8. The bore IE5 is connected to one end of the cylinder 54 by a port I and to the opposite end by a port I22, and each end of the bore is sealed by a rubber annular gasket or'bumper I24. Each end of the'bore is connected to a passage I25 in the associated head 52, said passage terminating in a chamber I28 containing a valve I39 urged to closed position by a spring I32 adjustably compressed by a cap I34 threaded into the head. The valve I32 is engaged by an actuator rod I36 extending through a complementary opening in the head and projecting into the cylinder 54 whereb upon engagement of the piston 58 with the rod I36,

the valve I is urged to open position against the'resistance of spring I32 exhausting the air within thepassage E26 to an exhaust or discharge port I38. V 7

With the stem IEM in the position shown in Figure 2, compressed air is delivered to each end of the bore I by passages I45 and I42 through the stem and compressed air is delivered to the port I22 urging the piston 58 to the left, as seen in Figure 1, forcing air from the cylinder 54 through the port I20 into the discharge line II6. When the piston 58 engages the rod I35 at the left of Figure 2, the rod actuates the valve I30 to openposition exhausting the left end of the bore I00 whereupon the pressure at the opposite end thereof is effective to urge the valve stem I54 against the bumper I24 at the left end of the bore. Under these conditions compressed air is delivered from the bore I to the port I28 and the piston 58 is urged to the right forcing air from the cylinder 54 through the port 22 and the discharge line I I8 until the piston 53 engages the rod I36 (not shown) at the right end of the cylinder whereupon the action is reversed and the piston 58 is urged again to the left. Thus it will be understood that upon delivery of compressed air to the line 42, the piston 58 is automatically and continuously reciprocated within the cylinder 54 to operate the units 36 which alternately suction hydraulic fluid from the line 32 and discharge the fluid under pressure to the line 38 until the ram 6- has developed the predetermined pressure against the Work.

As above noted, after completion of the cycle, the line 42 is exhausted and thereafter the exhaust valve stem I6 of the exhaust chamber 92 is opened to accommodate discharge of the pressure fluid within the cylinder 4 to the tank 28.

I claim:

I 1. In an actuating circuit for a hydraulic motor having a cylinder and a ram therein; the combination of aclosed reservoir of hydraulic fluid, a hydraulic intensifier having a discharge side connected to said cylinder and having a suction side connected to said reservoir, said intensifier being adapted upon actuation thereof to continu-- 5, ously deliver hydraulic pressure fluid to said cylinder, pneumatic motor means for continuously operating said intensifier as long as pneumatic pressure fluid is delivered to said motor means, an hydraulic valve comprising a casing having a chamber connected at all times to the intensifier and to the reservoir, said casing comprising a port connecting the chamber to the cylinder, and said valve comprising a stem and spring means for urging the stem to closed position Whereat said port is closed, means for movin said stem to open position against the resistance of said spring means, and pneumatic valve means operable in one position thereof to deliver pneumatic pressure fluid only to said reservoir whereby, upon opening of said stem, hydraulic fluid is forced from said reservoir to said cylinder, said pneumatic valve means being adapted in another position thereof to deliver pneumatic pressure fluid to said motor means, and being adapted in neutral position to exhaust both said reservoir and said motor means.

2. In an actuating circuit for a hydraulic motor having a cylinder and a ram; the combination of a closed reservoir of hydraulic fluid, a reciprocating hydraulic intensifier having a discharge side connected to said cylinder and having a suction side connected to said reservoir, said intensifier being adapted on one stroke thereof to draw fluid from the reservoir and on another stroke to force fluid to said cylinder, pneumatic motor means for continuously reciprocating said intensifier as long as pneumatic pressure fluid is delivered to said motor means, an hydraulic valve comprising a casing with a chamber connected at all times to the intensifier and to the reservoir, said valve casing comprising a port connecting the valve chamber to the cylinder, and said valve comprising a stem for closing said port and spring means for urging the stem to closed position, means for moving said stem to open position against the resistance of said spring means, said stem having an opening area acted upon by pressure of hydraulic fluid in said valve chamber and having a closing area greater than said opening area, said closing area being acted on by pressure of hydraulic fluid in said cylinder, and pneumatic valve means operable in one position thereof to deliver pneumatic pressure fluid only to said reservoir, said pneumatic valve means being adapted in another position thereof to deliver pneumatic pressure fluid to said motor means, said pneumatic valve means being adapted in a third position thereof to exhaust said intensifier and said motor means.

ROBERT K. SEDGWICK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 153,296 Atkinson July 21, 1874 2,371,450 Langdon Mar. 13, 1945 2,403,912 Doll July 16, 1946 

